1. Field of the Invention
The present invention relates to a device to aid drivers of vehicles, truck drivers in particular, in backing the vehicle to a desired spacing from another object.
2. Description of Related Art
Vehicle drivers, particularly drivers of tractor-trailer vehicles or other trucks, are frequently required to back the vehicle into a parking space or loading dock. In the case of a loading dock, the trailer or truck must be backed into substantial contact, or into a very close spacing, with the loading dock, so that freight can be loaded and/or unloaded from the vehicle. This docking requirement, in the past, has led to numerous instances in which the wall of the loading dock, and/or the trailer, are damaged by the truck making contact at a slightly elevated speed, because the driver is unaware, until making contact, of the distance between the truck and the dock. Resilient dock bumpers tend to decrease this problem, but still provide little or no indication to the driver that the truck is nearing contact with the dock, as the bumpers readily compress and no impact is felt. The bumpers also do not provide a distance indication.
Devices have heretofore been proposed in the art for use in assisting the driver of a vehicle in backing the vehicle toward another object. One of these, disclosed in U.S. Pat. No. 1,418,034, issued to Tennent, provides an indicator to alert the driver of the distance between the body of the vehicle and an object to the rear of the vehicle. That device has significant disadvantages that would essentially prevent its use on modern-day cars and trucks. The Tennent device relies on the use of a retractable or compressible bumper in gauging the distance, and, with the current laws mandating the use of impact-resistant bumpers, a bumper that is designed to retract or compress at very low speeds is likely to be illegal. Further, a disadvantage of that design is that it relies on a cable system linking the bumper to the indicator in the passenger compartment of the vehicle, which, while possibly acceptable for cars, would not be acceptable for vehicles such as tractor-trailers, in which the tractor is separable from the trailer, and in many instances is used with numerous trailers.
Having an indicator in the passenger compartment, as shown in Tennent, is not as advantageous as it might first appear to be. In backing up a vehicle, the driver is generally looking outside the vehicle, either into the rearview mirror, or, more commonly, into the side view mirrors. This is particularly true of a driver backing a tractor trailer into, for example, a bay at a loading dock, in picking up or delivering the freight or cargo carried inside the trailer. The same is true of an automobile driver backing into a parking space between two other cars. If it were necessary to look in the passenger compartment to determine the current spacing between the rear of the vehicle and an approaching object, the driver would have to take his or her eyes off the mirrors, thus increasing the chances of inaccurately aligning the vehicle at the loading dock or in the parking space.
Other warning-type devices have been disclosed in the art, but generally do not provide any continuing indication of the decreasing distance between the vehicle and the object it is approaching. Examples of such devices can be found in U.S. Pat. Nos. 3,187,710 and 4,967,180. A sighting device is disclosed in U.S. Pat. No. 4,257,706, issued to Smith.
It is therefore a principal object of the present invention to provide a device to be mounted on a vehicle that will function as a distance gauge for use in alerting a driver backing up a vehicle of the distance between the rear of the vehicle and an object behind the vehicle.
It is a further important object of the present invention to provide a device that will provide a truck driver with ample advance warning of the decreasing distance between the rear of the truck and an object, such as a loading dock, so that the truck may be slowly and controllably backed into contact with the dock for loading and/or unloading freight or cargo.
It is an additional important object of the present invention to provide a vehicle mounted device providing a distance gauging function that is readily adaptable for effective use with vehicles of different sizes and constructions.
It is a further important object of the present invention to provide a rear distance gauging device that is viewable by the driver either in a side view mirror, or when the driver extends his or her head out the window and looks to the rear of the vehicle.